1. Field of the Invention
This invention relates generally to a treatment and ablation apparatus that includes a primary antenna inserted into or adjacent to a selected body mass, such as a tumor, with one or more side deployed secondary antennas which are actively coupled to the primary antenna, and more particularly to a multiple antenna RF treatment and ablation apparatus with one or more secondary antennas actively coupled to the primary antenna, with the primary antenna coupled to a feedback control device and energy source.
2. Description of the Related Art
Current open procedures for treatment of tumors are extremely disruptive and cause a great deal of damage to healthy tissue. During the surgical procedure, the physician must exercise care in not cutting the tumor in a manner that creates seeding of the tumor, resulting in metastasis. In recent years, development of products has been directed with an emphasis on minimizing the traumatic nature of traditional surgical procedures.
There has been a relatively significant amount of activity in the area of hyperthermia as a tool for treatment of tumors. It is known that elevating the temperature of tumors is helpful in the treatment and management of cancerous tissues. The mechanisms of selective treatment are not completely understood. However, four cellular effects of hyperthermia on cancerous tissue have been proposed, (i) changes in cell or nuclear membrane permeability or fluidity, (ii) cytoplasmic lysomal disintegration, causing release of digestive enzymes, (iii) protein thermal damage affecting cell respiration and the synthesis of DNA or RNA and (iv) potential excitation of immunologic systems. Treatment methods for applying heat to tumors include the use of direct contact radio-frequency (RF) applicators, microwave radiation, inductively coupled RF fields, ultrasound, and a variety of simple thermal conduction techniques.
Among the problems associated with all of these procedures is the requirement that highly localized heat be produced at depths of several centimeters beneath the surface of the skin. RF applications may be used at depth during surgery. However, the extent of localization is generally poor, with the result that healthy tissue may be harmed.
With RF lesion making, a high frequency alternating current flows from the electrode into the tissue. Ionic agitation is produced in the region of tissue about the electrode tip as the ions attempt to follow the directional variations of the alternating current. This agitation results in frictional heating so that the tissue about the electrode, rather than the electrode itself, is the primary source of heat. Tissue heat generated is produced by the flow of current through the electrical resistance offered by the tissue. The greater this resistance, the greater the heat generated.
Lesion size ultimately is governed by tissue temperature. Some idea of tissue temperature can be obtained by monitoring the temperature at an electrode or probe tip, usually with a thermistor. RF lesion heat is generated within the tissue, the temperature monitored will be the resultant heating of the electrode by the lesion. RF lesion heat is generated within the tissue, the temperature monitored is the resultant heating of the probe by the lesion. A temperature gradient extends from the lesion to the probe tip, so that the probe tip is slightly cooler than the tissue immediately surrounding it, but substantially hotter than the periphery of the lesion because of the rapid attenuation of heating effect with distance.
Current spreads out radially from the electrode tip, so that current density is greatest next to the tip, and decreases progressively at distances from it. The frictional heat produced from ionic agitation is proportional to current, i.e., ionic density. Therefore, the heating effect is greatest next to the electrode and decreases with distance from it. One consequence of this is that lesions can inadvertently be made smaller than anticipated for a given electrode size if the RF current level is too high. There must be time for equilibrium heating of tissue to be reached, especially at the center of the desired lesion volume. If the current density is too high, the tissue temperature next to the electrode rapidly exceeds desired levels and carbonization and boiling occurs in a thin tissue shell surrounding the electrode tip.
A need exists for an ablation apparatus with an electromagnetic energy source and a monopolar multiple antenna device. There is a further need for a monopolar multiple antenna device with a primary antenna, and one or more secondary antennas that are positioned in a lumen of the primary antenna, laterally deployable from the primary antenna into a selected tissue mass, with both antennas electromagnetically coupled to an electromagnetic energy source. It would be desirable to provide a monopolar method to ablate a selected tissue mass by introducing the primary antenna into the selected mass, deploying a distal end of the secondary antenna into the selected mass, and applying electromagnetic energy to the primary and secondary antennas.
Accordingly, it is an object of the invention to provide an ablation device which includes a monopolar multiple antenna.
Another object of the invention is to provide an ablation apparatus with a monopolar multiple antenna device including a primary antenna that pierces and advances through tissue, a secondary electrode positioned in a primary antenna lumen that is laterally deployable from the primary antenna into a selected tissue mass.
Yet another object of the invention is to provide an ablation apparatus with a monopolar multiple antenna device, including primary and secondary antennas that are each electromagnetically coupled to an electromagnetic energy source.
A further object of the invention is to provide a method for ablating a selected tissue mass utilizing a monopolar multiple antenna device.
These and other objectives are achieved in an ablation treatment apparatus. The apparatus includes an ablation energy source producing an electromagnetic energy output. A monopolar multiple antenna device is included and has a primary antenna with a longitudinal axis, a central lumen and a distal end, and a secondary antenna with a distal end. The secondary antenna is deployed from the primary antenna central lumen in a lateral direction relative to the longitudinal axis. The primary antenna and secondary antennas are each electromagnetically coupled to the electromagnetic energy source.
In another embodiment, a method of ablating a selected tissue mass is provided utilizing a monopolar multiple antenna device.
The monopolar multiple antenna device can be an RF antenna, a microwave antenna, a short wave antenna and the like. At least two secondary antennas can be included and laterally deployed from the primary antenna. The secondary antenna is retractable into the primary antenna, permitting repositioning of the primary antenna. When the multiple antenna is an RF antenna, it can be operated in monopolar or bipolar modes, and is capable of switching between the two.
One or more sensors may be positioned at an interior or exterior of the primary or secondary antennas to detect impedance or temperature. A feedback control system is coupled to each of the sensors, the electromagnetic energy source and the primary and secondary antennas.
An insulation sleeve can be positioned around the primary and secondary antennas. Another sensor is positioned at the distal end of the insulation sleeve surrounding the primary antenna.
The feedback control device can detect impedance or temperature at a sensor. In some embodiments, the feedback control system can include a multiplexer. Further, the feedback control system can provide an ablation energy output for a selected length of time, adjust ablation energy output and reduce or cut off the delivery of the ablation energy output to the antennas. The feedback control system can include a temperature detection circuit which provides a control signal representative of temperature or impedance detected at any of the sensors. The feedback control system can also include a microprocessor connected to the temperature detection circuit. Initially, temperature, ablation duration and energy level are selected and manually input into the feedback control system. As process parameters change, the initial manually input values are then automatically modified by the feedback control system to achieve the desired level of ablation without impeding out, and minimize the ablation of non-targeted tissue.
Further, the multiple antenna device can be a multi-modality apparatus. One or all of the antennas can be hollow to receive an infusion medium from an infusion source and introduce the infusion medium into the targeted tissue mass.